1. Field of the Invention
The present invention relates to an image reproducing apparatus, an image reproducing method and a computer readable storage medium for receiving input image data, and outputting and reproducing an image having a greater number of gradation levels than that of the above-mentioned image data.
More particularly, the present invention refers to a technique for improving smoothness of an image that is output, by increasing the number of gradation levels of the above-mentioned image data, when carrying out an output process, such as a printing process of an image using a printer.
2. Description of the Related Art
When a printing process of a full color image is performed using a printer, image data having 256 gradation levels for each of four primary colors of C, M, Y and K are usually used as input data. In other words, image data consisting of 8 bits of gradations for each color (thus, image data of 24 bits in total) are usually input. However, when a printing process is actually performed with 256 gradation levels for each color, the step between different gradation levels may sometimes become visible in a highlighted portion in which luminance of image data is relatively high (that is, portion in which density of image data is low). A possible reason for this is that 256 gradation levels may be inadequate for smooth reproduction of an image since the sensitivity of human eye is relatively high in such a highlight portion.
In order to deal with such a situation, a simple solution is to increase the number of gradation levels of input image data, that is, to use a relatively high number of gradation levels, such as 1024 gradation levels or 4096 gradation levels for each color. It is possible to reproduce a smooth image in which the step between different gradation levels is no longer visible by inputting image data having a relatively large number of gradation levels.
However, the total amount of image data will increase with the increase in the number of gradation levels of the input image data.
Further, the increase of total amount of image data gives rise to another problem that memory capacity needs to be increased in order to store the above-mentioned image data, and the processing time required to process the above-mentioned large amount of image data is also increased.
In addition, with the increasing amount of data it will be also required to expand the means for preparing the relatively large amount of image data and the means for developing the above-mentioned image data, correspondingly, so that the overall size of the apparatus for executing data processing will increase, leading to another problem of an increase in the production cost.